text: Metal nitrido complexes are coordination compounds and metal clusters that contain an atom of nitrogen bound only to transition metals.  These compounds are molecular, i.e. discrete in contrast to the polymeric, dense nitride materials that are useful in materials science.  The distinction between the molecular and solid-state polymers is not always very clear as illustrated by the materials LiMoN and more condensed derivatives such as NaMoN.  Transition metal nitrido complexes have attracted interest in part because it is assumed that nitrogen fixation proceeds via nitrido intermediates.  Nitrido complexes have long been known, the first example being salts of [OsON], described in the 19th century.